Page 110 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

Chapter 4: Conventional Survey 89
cardinal points are the easiest to use, because one can use a wrist compass to determine direction and a tape measure fixed at a convenient origin to measure the distance. By swimming survey lines in N, S, E, and W direc- tions, the extent of the site can be deduced quite simply. The results, plotted on a sketch map of the site, should give a fair idea of its approximate extent and dimensions. It may then be worthwhile to run the NE, SE, SW, and NW directions to fill in more information. There are, naturally, many other ways to determine the perimeter of the site depending on its nature. It will be important to make a careful assessment of how best to do this given the conditions. For example, it may be possible to swim around the perimeter of a site measuring distance and bearing, or to measure from one side of the site to the other directly. The system chosen will depend on the local conditions, but the objective is to establish the approximate area of the site. It should be remembered that the area initially investigated may not, in fact, be the main part of the site, and that there might be other areas of compa- rable significance some distance away.
Various alternative approaches to deal with this present themselves. One option is to carry out an extensive survey of the general area. Another option is to concentrate on the main area with limited exploration in the neighborhood. A person could concentrate on a local survey, while carry- ing out a limited survey over a wider area with a small team. Whatever happens, work should always proceed systematically. The priorities will depend on the circumstances. Logical and simple solutions are of the essence; one is not trying to produce a plan of the site, simply an overview with some basic dimensions.
It is very useful to establish a baseline across the center of the site, prefer- ably along the long axis of the site (if there is one), as it can serve as a datum for further survey work and operate as an important orientation aid for the surveyors and others working on the site. It is best to use the baseline for rough or initial survey work as the points on it are not precise enough to serve as accurate survey stations. The ends of the baseline can act as per- manent reference points and should be fixed and marked so that even if the site survey is abandoned, the baseline can be relocated. It will also be necessary, if the baseline is long, to pin it or attach it in some way to the bottom, thus preventing bowing and reducing the effects of currents.
It is advisable to use a tape measure or a marked line. A number of two- dimensional survey options exist to develop and refine this first-order survey. These are discussed next. The choice of method will be subject to the nature of the site and the preferences of the surveyor.
It is suggested that proper underwater writing slates are constructed with removable sheets that can be stored in a file (see Chapter 9). After each